Un-stacking textures that are stacked over each other
If you still want to do this after reading pie75's answer, the MultiEdit Addon   might come in handy. 


Select all objects, go to MultiEditMode.
Then select a face, press Shift+G -> Image
Move the UVs in UV Editor by pressing G X 256 (in this case, other value might be needed for other cases).
Hide the faces with H and proceed with another yet unhidden face, but this time move for the double amount.
When all UVs are moved, exit MultiEditMode and you are done.


Blenderman example (without hiding faces):